Systems for transferring a pneumatic pressure from a fixed conduit to a rotating conduit are known, wherein a hollow rotating output shaft is rotatably coupled to a hollow fixed input shaft, and wherein one or more annular gaskets are arranged in permanent seal contact with both the input shaft and the output shaft, in order to prevent or reduce a leakage of transferred fluid or pressure into the gap between the two shafts.
The above-mentioned prior art has the drawback that the sealing gaskets are worn due to the sliding friction between the input and output shafts. This involves the need to have to frequently replace them in order to avoid or reduce the fluid leakages due to an excessive wear, but this often requires very high costs, due not only to the cost of the sealing gaskets, which may be high as such, but especially due to the labor costs to disassemble the device in which they are mounted, for example, a wheels-hub unit of a heavy vehicle, for example, a truck or articulated truck.
Another drawback of the prior art is that the gaskets, which are in continuous sliding contact with the stationary conduit and/or with the rotating conduit with respect to the stationary one, suffer from the operative temperature, thus involving a worsening of the sealing ability performance. In fact, under reduced operative temperatures in cold environments, such gaskets tend to increase the rigidity thereof, accelerating the friction wear process thereof and reducing the seal.
The absence of a wear control of such gaskets could cause leakages of the fluid to be transferred from the inlet conduit to the outlet conduit.
Furthermore, such gaskets tend to stiffen upon time, even if they are not used, thus worsening the sealing ability.